Apparatus for producing acetylene by the pyrolysis of a suitable hydrocarbon



Sept. 9, 1958 Filed Ma rch v4, '1952 C. J. COBERLY ET AL APPARATUS FORPRODUCING ACETYLENE BY THE PYROLYSIS OF A SUITABLE HYDROCARBON 2Sheets-Sheet 1 /NVN7'O/?$. Cmmsmc: d. COBERLY CHARLES WHEELER COBERLY BYTHE/l? ATTORNEYS- gHRRIS, K/ECH, FOSTER 6 HARRIS Sept. 9, 1958 J.COBERLY EI'AL 2,851,340 APPARATUS FOR PRODUCING ACETYLENE BY THEPYROLYSIS OF A SUITABLE HYDROCARBON Filed March 4, 1952 2 Sheets-Sheet 2m; J? 36 ,,:Z \3 2 34 f; 3

4p 7 36 1 C r 36 6/ a! F HARRIS, Klacl-l, Foam/e & Helm/s 6v UnitedStates Patent APPARATUS FOR PRODUCING ACETYLENE BY 11113 PYRQLYSIS OF ASUITABLE HYDROCAR- Clarence J. Coberly, Los Angeles, and Charles WheelerCoberly, Pasadena, Calif., assignors to Wultf Process Company,Huntington Park, Califl, a corporation of California Application March4, 1952, Serial No. 274,752 2 Claims. (Cl. 23-277) Our invention relatesto the art of producing acetylene by the pyrolysis of otherhydrocarbons. It is well known in the art that if a suitable hydrocarbonis raised to reaction temperature at least a portion of the hydrocarbonwill be. converted to acetylene, but it is also well known that if thehot acetylene is then cooled slowly, the acetylene decomposes into freecarbon and hydrogen, releasing considerable heat.

It is an object of our invention to provide a process by, and anapparatus in, which acetylene can be formed by the pyrolysis of asuitable hydrocarbon and by, and in, which the acetylene so formed canbe recovered with very little, if any, decomposition.

To produce acetylene by the pyrolysis of a suitable hydrocarbon, largeamounts of heat must be supplied to produce the necessary endothermicreaction, this heat being hereinafter referred to as reaction heatwhich, of course, is eventually latent heat in the acetylene. An almostequal amount of heat is needed to raise the ingas to reactiontemperature, this heat being hereinafter referred to as sensible heat.This heat is carried as sensible heat in the oil-gas produced by thereaction and must be rapidly removed from the off-gas by cooling theoff-gas, if any substantial proportion of acetylene is desired as afinal product.

It is a further object of our invention to provide a process and anapparatus in which the oil-gas is not only rapidly cooled, but in whicha large proportion of the sensible heat so removed from the off-gas isretained in the apparatus and re-used to supply sensible heat to them-gas.

It is not particularly difficult to provide a process and apparatuswhich will produce an oif-gas containing some acetylene but it is onlyby providing an apparatus having definite proportions andcharacteristics and operating this apparatus within definite limits thatan oil-gas containing a substantial proportion of acetylene can beproduced.

It is a further object of our invention to provide an apparatus of suchproportions and characteristics, and to provide a process operatingwithin such limits, that an off-gas containing a substantial proportionof acetylene can be produced from an in-gas containing a substantialproportion of a suitable hydrocarbon.

The term suitable hydrocarbon, as used herein to denote a hydrocarboncapable of producing acetylene, is hereby defined as including all thosehydrocarbons, and

limited to only those hydrocarbons, which were known.

in the art, at the time the application for this patent was filed, to becapable of forming acetylene by pyrolysis. Any such hydrocarbon can, ofcourse, be used, but the selection of this hydrocarbon depends uponavailability and cost. Natural gas, at points where it is available, isat this time probably the cheapest suitable hydrocarbon, but butane,popane and ethane are more economical in some localities.

The term substantial proportion, wherever used herein to denote theproportion of gas in any mixture,

Patented Sept. 9, 1958 is hereby defined as a proportion of at least twopercent (2%) by volume of the total mixture.

The term in-gas is hereby defined as a gas consisting largely orpartially of a suitable hydrocarbon which is delivered to the reactionzone in which conversion to acetylene occurs.

The term off-gas is defined as the gas mixture which contains acetyleneas it leaves said reaction zone.

The term ignition temperature, as used herein, is defined as thetemperature at which the suitable hydrocarbon will break down to releasehydrogen and thus initiate combustion in the presence of oxygen. Propaneso breaks down at about 600 C. and methane breaks down at about 900 C.The ignition temperature of F practically all suitable hydrocarbons isknown in the art or can be easily determined by a person skilled in theart.

The term reaction temperature, as used herein, is defined as thetemperature at which the suitable hydrocarbon is molecularly convertedfrom its original state into acetylene. The reaction temperature ofpropane is about 900 C. and the reaction temperature of methane is about1200 C. The reaction temperatures of many suitable hydrocarbons areknown in the art or can be easily determined by a person skilled in theart.

The term non-flammable mixture is used herein to denote a mixture ofgases containing a hydrocarbon and oxygen in which the amount of oxygenpresent is substantially less than that needed for complete combustionof the hydrocarbon.

Complete combustion of a hydrocarbon, wherever used herein, is definedas a combustion in which the hydrocarbon is converted to carbonmonoxide, carbon dioxide and water. Incomplete combustion of any ingaswhich contains a hydrocarbon is defined as a combustion which leavessome hydrocarbon in the off-gas.

Further objects and advantages will be set forth hereinafter.

The apparatus used is disclosed in Figs. 1 to 6 in which:

Fig. l is a perspective view of this furnace;

Fig. 2 is a section therethrough;

Fig. 3 is a section therethrough on a plane represented by the line 33of Fig. 2, this plane being viewed in the direction of the arrowsadjacent the ends of this line;

Fig. 4 is a section therethrough on a plane represented by the line 4-4of Fig. 2, this plane being viewed in the direction of the arrowsadjacent the ends of this line;

Fig. 5 is a section through the wall of the furnace and through a gasnozzle projecting into a hole through said wall; and

Fig. 6 is a diagram of the apparatus including furnace, valves andpiping.

In the following specification and claims, the abbreviations RH forright-hand and LH for left-hand are freely used to denote the positionof parts as seen in the drawings.

The furnace shown in the drawings is primarily one in which hightemperature endothermic reactions may be carried on. The furnace is welladapted to the conversion of any suitable hydrocarbon to anotherhydrocarbon, for example, the conversion of methane to acetylene.

The furnace consists of a gas-tight steel shell 10 having a heatrefractory lining 11 offire brick or the like. Placed inside are tworefractory masses, an LH mass 12 and an RH mass 13. The masses may bemade of alundum silicon carbide or zirconium oxide. The masses must bemade of material that, over long periods, will withstand temperaturessomewhat in excess of 1500 C. without material injury. The masses 12 and13 have small cylindrical channels 14, shown in Fig. 3, extendingtherethrough in a direction substantially parallel to the major axis 66of the furnace. These channels 14 may 3 be one-half inch /2 in.) or lessin diameter and are substantially straight and unimpeded. The two masses12 and 13 divide the interior of the furnace into three chambers,namely, an LH end space 15, a central space 16, and an RH end space 17.

An LH off pipe 18 takes or delivers gas to the LH end space and an RHoli pipe 20 takes 51- delivers gas to the RH end space 17. A perforateddispersion plate 19 spaced away from the inside end of the shell on rods21 is provided at both ends of the furnace to give a more evendistribution of the in-gas to the channels 14 in both masses 12 and 13.p

A central ofi pipe 22 having a valve 23 takes gas from or delivers gasto the top of the central space 16. Project- 'ing into each side of thefurnace in a plane close to the inner face of each of the masses 12 and13 is a series of nozzles. The LH series 31 is in a plane close to theinner or RH face of the LH mass 12, and the RH series 32 is in a planeclose to the inner or LH face of the mass 13. In a small furnace therewill be five nozzles 33 to each series of nozzles 31 and 32, three onone side of the furnace and two on the other, as shown in Fig. 4 of thedrawings. Each of the nozzles 33, as shown in Fig. 5, is inserted in anopening 34 in the lining 11 of the furnace, the head 35 of the nozzlebeing welded to the shell 10 of the furnace inside a manifold 36 whichis also welded to the shell 10. The two. manifolds of series 31 and 32,one'on each side of the furnace, are connected by pipes 37 so that allthe nozzles 33 of each series may be supplied with gas through asuitable valve. Gas under pressure is jetted through the small orifices39 of the nozzles 33 at high velocity and forms a sheet of gas parallelto the end of each mass and the gas from the channels 14 impinges onthis sheet at right angles thereto. We have found that this arrangementgreatly facilitates rapid and complete mixing of the gases which isnecessary in any reaction which may be performed in the furnace. Inmaking acetylene, the total time the mixed gases are at reactiontemperature must be less than one-tenth (1/10) of a second. An opening40 provided with a tight lid or cover is provided in'the side of thefurnace so that a torch may be used to initiate combustion in thecentral space 16 whenever the furnace is started cold.

We have found it necessary to place the furnace with its major axishorizontal if it is to be used with high temperature reactions takingplace in the central space 16. By placing the furnace with its axishorizontal and with the channels 14 also-horizontal, the hot masses 12and 13 may be supported on their sides on the lining 11 and no metalsupports for the masses 12 and 13 are necessary. This is important sinceany metal of reasonable cost would be melted or perhaps vaporized atfurnace temperatures, or might act catalytically to produce undesirableresults. 1

The furnace shown and described herein may be used for many purposes,particularly, for example, to produce acetylene from a suitablehydrocarbon, for example, methane, ethane, propane, or butane. Acetylenecan be so produced by various processes which may be conducted in thisfurnace, for example, by a process which may be described as follows.

When the furnace above described is to be used to conduct thisparticular process, additional parts must be provided to make a completeapparatus which may be described as follows.

The pipes 37 forming parts of the nozzle assemblies 31 and 32 areconnected through valves 51 and 52 to an air pipe 53 which is preferablyconnected to a preheater 54 which is supplied with cold air through apipe 55. Preheated air is not absolutely essential to the process andthe heater 54 will probably not be used in many installations. The pipe18 maybe connected through a valve 56 with a oif-gas pipe 57 or througha valve 58 with an in-gas pipe 59. The pipe 20 may be connected througha valve 60 with the off-gas pipe 57 or through a valve 61 with thein-gas pipe 59. In-gas is produced in a mixer 70, a suitable hydrocarbonbeing delivered to the mixer 70 through a valve 71, air being deliveredthrough a valve 72 and a diluent such, for example, as steam beingdelivered through a valve 73.

Gases may be drawn from the apparatus through the pipe 57 by anexhauster which may pull a substantial vacuum on the interior of thefurnace shell 10. In some furnaces it is desirable to inject water intothe spaces 15 and 17 through pipes 81.

Suitable thermocouples, not shown, are provided at various points in thefurnace, and suitable timing devices are provided for actuating thevarious valves, all of which are power operated. The furnace is heatedas a preliminary step to cyclic operation. This heating can beaccomplished by starting the exhauster and opening at least one of thevalves for example the valve 56, all other valves being closed, andinserting a torch through the opening 40 so that the products ofcombustion from the torch are drawn from the central space 16 throughthe LH mass 12 and out through the pipe 18, the valve 56 and the pipe 57by the exhauster 80. This heating is ordinarily conducted slowly whichis not objectionable since once heated the furnace may be operated undercyclic conditions over a long period without reheating. In practice amore elaborate arrangement may be provided for preheating but since thispreheating forms no part of the invention, it need not be morespecifically described.

The cyclic operations may be described as starting with the LH mass 12preheated so that its RH end is at a temperature above 1200 C. and itsLH end is at a substantially lower temperature. The cycle will consistof an RH flow in which gas flows from the space 15 toward the space 17and an LH flow in which gas flows from the space 17 toward the space 15.During the RH flow the valves 51, 58, 60, 71, 72, and 73 are open andthe exhauster 80 is drawing gas through the furnace. The valves 71, 72,and 73 which are left open during the entire cycle are set to produce anin-gas in the pipe 59 consisting of the suitable hydrocarbon, sufficientair or oxygen to provide for the complete combustion of only a portionof the suitable hydrocarbon, plus some steam.

In large plants oxygen may be supplied through the valve 71 and throughthe pipe 55 instead of air, in which case the amount of oxygen suppliedmust be correspondingly restricted. The in-gas delivered through thepipe 59 is non-flammable in smallpassages such as the channel 14 whencold, but it will burn when the entire mass of the in-gas is heatedabove the ignition point. It is so heated by transfer from the LH massand when it has been heated above the ignition temperature in channels14, a limited and partial combustion occurs, followed by a partialdecomposition of the hydrocarbon. The amount of air or oxygen injectedthrough the nozzles 33 may be sufiicient to provide for the completecombustion of from 10% to 40% of the suitable hydrocarbon delivered tothe mixer 70 through the pipe 71.

The temperature in the central space 16 will then probably not exceed1300 C. with propane in-gas, or 1500 C. with methane in-gas. At thesetemperatures a portion of the hydrocarbon is converted into acetylene.It is important, however, to operate the apparatus so that there is onlya partial conversion and the off-gas contains a substantial proportionof hydrocarbons other than acetylene. In other words, the furnace mustbe operated so there is not only partial combustion of the hydrocarbon,but also this partial combustion must be controlled to give a maximumamount of the desired products in the off-gas. The conversion of thehydrocarbon in-gas to acetylene increases with temperature, but as theamount of combustion is increased to obtain the higher temperature,it'reduces the hydrocarbon available for conversion to acetylene, andthese two opposite variables must be controlled to obtain optimumresults. For a given size and design, this optimum can be correlatedwith temperature, and the operator must control the amount of air oroxygen supply to maintain this temperature.

The in-gas should have a velocity in the channels of from 30 to 120pounds per square foot area of the channels. This mass velocity limitapplies to all in-gas regardless of its composition. The air injectedthrough the nozzles 33 should have an even higher velocity. To obtain anoff-gas containing a substantial proportion of acetylene, the volume ofthe central space 16 depends upon the composition of the in-gas, theoperating temperature, and the mass velocity. We have found that thevolume should be from to 40% of the total volume of all channels 14 inboth masses 12 and 13. The ratio of volumes of steam to hydrocarbon inin-gas may be from 1.0 to 6.0. The RH flow must be stopped before the RHend of the LH mass 12 becomes so cooled that partial combustion does notoccur therein. The point at which the RH flow must be stopped can bereadily determined by a thermocouple near the RH end of the LH mass andthe flow can be continued until this temperature falls to, say, 1000 C.which may take several minutes. In practice, the timer is set to stopthe RH fiow in from one to four minutes after it is started. During thisRH flow the LH end of the LH mass is cooled by the flow of in-gastherethrough and the entire RH mass 13 is heated as it cools theofi-gas. The RH flow must, however, also be stopped before the ofi-gasdelivered to the pipe 20 reaches a temperature at which acetylene isunstable. In practice this temperature is assumed, for safety, to be 450C. In some plants it is desirable to inject a small stream of water intothe space 17 during RH flow and into the space during LH flow. Thevaporization of this water, of course, lowers the temperature of theoff-gas.

The RH flow is stopped by closing the valves 58, 60 and 51 and the LHflow is started by opening the valves 56, 61, and 52. These valvechanges are made automatically and very quickly so that the flow ofgases into, through, and out of the furnace is interrupted for less thanone second. The LH flow from the pipe to the pipe 18 after the aparatushas operated cyclically for a few minutes is exactly like the RH flowexcept conditions are reversed. The in-gas picks up heat stored in theRH mass during RH flow and the off-gas delivers heat to the LH mass.

The apparatus can, of course, be used to practice various processes. Thepreferred process is that above described and this process may be usedto convert an in-gas containing any suitable hydrocarbon to an olf-gascontaining a substantial proportion of acetylene. This process can beapplied to the conversion of methane or a gas such as natural gas to anoff-gas which contains a substantial amount of acetylene. The processoperates very well when applied to the olefines which react to acetyleneat lower temperatures than methane.

We claim as our invention:

1. A furnace for subjecting gases to endothermic reactions comprising: asingle gas-tight shell having a single heat insulating lining disposedabout a single central longitudinal axis; two regenerative masses insidesaid lining and dividing the space into two end spaces and a centralspace, the inner ends of said masses defining said central space beingsubstantially parallel and perpendicular to said axis each of saidmasses having channels passing horizontally therethrough and connectingone of said end spaces with said central space the two masses beingplaced symmetrically about said axis; a conduit so placed as to eitherdeliver an in-gas to the LH end space or to withdraw an off-gas fromsaid space; a conduit so placed as to either deliver an in-gas to the RHend space or withdraw an off-gas from said space; a series of nozzles soplaced as to inject streams of gas into said central space close to theRH end of said LH mass; and a second series of nozzles so placed as toinject streams of gas into said central space close to the LH end ofsaid RH mass, all of said nozzles in each of said series beingsubstantially parallel and in a transverse plane in said central spaceparallel and close to the said inner end of one of said masses so as toblend said streams of gas from all of the nozzles in each of said seriessubstantially into a single sheet of gas in said plane.

2. A furnace as specified in claim 1 in which some of the nozzles ineach of said series of nozzles are directed into said central space fromone side of the furnace and the remaining nozzles in that series aredirected into said central space from the other side of said furnace.

References Cited in the file of this patent UNITED STATES PATENTS1,711,273 Manker Apr. 30, 1929 1,900,396 Isley Mar. 7, 1933 1,965,770Burgin July 10, 1934 2,208,123 Duncan July 16, 1940 2,232,121 LinderFeb. 18, 1941 2,319,679 Hasche May 18, 1943 2,351,661 Carter June 20,1944 2,377,245 Krejci May 29, 1945 2,423,374 Chaney July 1, 19472,552,277 Hasche May 8, 1951 FOREIGN PATENTS 572,893 Germany Mar. 25,1933 583,851 Germany Sept. 13, 1933 578,311 Germany June 12, 1933605,640 Germany Nov. 20, 1934 458,692 Great Britain Dec. 24, 1936

1. A FURNACE FOR SUBJECTING GASES TO ENDOTHERMIC REACTIONS COMPRISING: ASINGLE GAS-TIGHT SHELL HAVING A SINGLE HEAT INSULATING LINING DISPOSEDABOUT A SINGLE CENTRAL LONGITUDINAL AXIS; TWO REGENERATIVE MASSES INSIDESAID LINING AND DIVIDING THE SPACE INTO TWO END SPACES AND A CENTRALSPACE, THE INNER ENDS OF SAID MASSES DEFINING SAID CENTRAL SPACE BEINGSUBSTANTIALLY PARALLEL AND PERPENDICULAR TO SAID AXIS EACH OF SAIDMASSES HAVING CHANNELS PASSING HORIZONTALLY THERETHROUGH AND CONNECTINGONE OF SAID END SPACES WITH SAID CENTRAL SPACE THE TWO MASSES BEINGPLACED SYMMETRICALLY ABOUT SAID AXIS; A CONDUIT SO PLACED AS TO EITHERDELIVER AN IN-GAS TO THE LH END SPACE OR TO WITHDRAW AN OFF-GAS FROMSAID SPACE; A CONDIUT SO PLACED AS TO EITHER DELIVER AN IN-GAS TO THE RHEND SPACE OR WITHDRAW AN OFF-GAS FROM SAID SPACE; A SERIES OF NOZZLES SOPLACED AS TO INJECT STREAMS OF GAS INTO SAID CENTRAL SPACE CLOSE TO THERH END OF SAID LH MASS; AND A SECOND SERIES OF NOZZLES SO PLACED AS TOINJECT STREAMS OF GAS INTO SAID CENTRAL SPACE CLOSE TO THE LH END OFSAID RH MASS ALL OF SAID NOZZLES IN EACH OF SAID SERIES BEINGSUBSTANTIALLY PARALLEL AND IN A TRANSVERSE PLANE IN SAID CENTRAL SPACEPARALLEL AND CLOSE TO THE SAID INNER END OF ONE OF SAID MASSES SO AS TOBLEND SAID STREAMS OF GAS FROM ALL OF THE NOZZLES IN EACH OF SAID SERIESSUBSTANTIALLY INTO A SINGLE SHEET OF GAS IN SAID PLANE.